Provide non-async overload to RespondWith

[TheRealPiotrP]

Current implementation forces async, which will result in warning:
file: 'file://foo.cs'
severity: 'Warning'
message: 'This async method lacks 'await' operators and will run synchronously. Consider using the 'await' operator to await non-blocking API calls, or 'await Task.Run(...)' to do CPU-bound work on a background thread. [Project]'
at: '338,73'
source: ''